This invention relates to a two-part latex adhesives for dry bonding a polyether urethane foam to rigid or semi-rigid substrates such as styrene board and fiberglass.
Urethane foam has insulating and cushioning properties which are useful in various applications. The urethane foam is laminated to various rigid or semi-rigid substrates which can be used in the manufacture of furniture and construction materials, such as automotive headliners. In the past solvent-borne adhesives have been used in preparing the laminates. However, there has been an ongoing trend to replace solvent-based adhesives such as urethanes, chloroprenes, acrylonitrile-butadiene rubbers, and the like with aqueous adhesives. The aqueous emulsion adhesives which have been developed include, for example, chloroprene latices, ethylene-vinyl acetate copolymer emulsions, and acrylic emulsions.
Japan. Kokai 56-185532 (issued May 24, 1983 to Y. Huseya et al.) describes an aqueous adhesive useful for wet lamination of various substrates to a polyurethane foam. It contains 100 parts of a vinyl emulsion polymer (having a Tg within the range of -40.degree. C. to +40.degree. C.) containing 1-20 parts of an unsaturated acid monomer (e.g., carboxylic, sulfonic, or phosphate groups), 0.4-10 parts of an alkaline metal compound (e.g., potassium or sodium hydroxide, sodium acetate, sodium phosphate, sodium formate, sodium chloride, and preferably potassium or sodium carbonate, typically as a 5-30 wt. % aqueous solution), 2-40 parts of a compound having at least two epoxy groups in the molecule (e.g., an aqueous dispersion of polyhydric alcohol glycidyl compound or glycidyl ether type epoxy resin, and optionally 0.4-10 parts of a silane coupling agent (e.g., vinyl triethoxy silane or gamma-glycidoxypropyl methoxy silane). The inclusion of the acid monomer and the alkaline metal chemical increases heat-resistance. Both a high degree of heat-resistance and water-resistance are required for materials used in automobile interiors. Addition of the silane coupling agent reportedly improves the heat-resistance and water-resistance to meet the requirement for automobile interior use.
As the automotive industry is switching from polyester urethane to polyether urethane foams for automotive interior use (e.g., for headliners) because of their better humidity resistance, there is a need for a latex adhesive suitable for providing laminates with the required properties, i.e., good water- and heat-resistance and good adhesion.